Manufacture of artificial threads from viscose



Ap fl 1936a A. ZIMMERMANN 11m, 2,036,313

MANUFACTURE OF ARTIFICIAL THREADS FROM VISCOSE Filed Jan. 18, 1932 Will Patented Apia 7, 1936 NITE'D STATES PATENT OFFICE MANUFACTURE OF ARTIFICIAL THREADS FROM VISCOSE Main, Germany Application January 18, 1932, Serial No. 5873M In Germany January 22, 1931 ii (llalms.

Qur present invention relates to the manu facture of artificial silk threads of high tenacity and high extensibility.

One of its objects is to provide a process for obtaining such threads. Another object are the new threads obtainable by our new process. Still another object is the apparatus for obtaining our new threads. Further objects will be seen from the detailed specification following hereafter, reference being made to the accompanying drawing in which Fig. 1 shows diagrammatically a device for obtaining threads having high tensile strength and high extensibility and Fig. 2 shows the same arrangement with another stretching device. The same reference characters indicate the same parts.

We have found that the elasticity of silks of high tenacity can'be influenced already during the spinning process merely by mechanical measures in such a favorable way, that the threads show a working capacity which is higher than that ofthe hitherto known artificial fibers made from viscose.

Our invention is based upon the observation that, when the spinning baths known for the production of silks oi high'tenacity are used, a thread drawn from the spinning bath in a stretched condition is strongly contracted when caused to enter into water while in a completely unstretched condition, that is to say while hanging freely, and when subsequently subjected to a second stretching, yields a thread which has a tenacity exceeding 2.5 grams per denier and an extensibility from above 9 to above 15 per cent. Also the extensibility of these threads in the wet state is at least just as high as, but mostly higher than that in the dry state. This observation is the more surprising ns it is directly contrary to the statements given in Die Kunstseide 1930, page 131, second column, namely that threads which are spun in strong sulfuric acid with or without stretching are completely irreversible in their longitudinal swelling when the sulfuric acid is removed by washing, for strong sulfuric acid baths form no exception to this observa tion. The said contraction also occurs in the case of spinning baths containing less than 50;- 55 percent of sulfuric acid monohydrate, which fact is likewise in contradiction to the statements git-en in the'above journal. The threads contracted by entering into water after the first stretching operation retain theirgood degree (ill. 18-54) of strength, even when dried without being stretched.

It has proved to be advantageous to draw the thread in the first stretching period, that is in the acid, wet state, so as to obtain a finer titre than is intended for the finished thread, then to allow it to shrink so as to assume a coarser titre than that which it is finally to have and, after it leaves the Water-bath in the second stretching period, to draw it out to its final titre. The amount of shrinking depends, inter alia, upon the amount of the stretching before-the contraction and increases with this stretching. When there is spun, for instance, in a bath according to the subjoined example ti and with a speed of draught of 50 metres, the thread contracts, when freely entering the water, by 50 per cent of its length. By increasing the stretching before the draught roller, this contraction may be increased to 61 per cent. When working under particularly favorable conditions it has been possible to obtain contractions exceeding per cent. The process is carried out, for instance, in the following manner: After leaving the bath, the thread is drawn off by a roller while passing over one or several glass rods, the roller having a greater peripheral velocity than corresponds with the final titre. From this roller the thread falls into a trough containing water through which it passes for a length of from 10 to 50 cm. completely loosely suspended, whereupon it is drawn out again by means of a second roller having a peripheral velocity which corresponds with the desired titre. Between this second roller and the water-bath there is interposed another stretching device composed of glass'rods. Instead of using stretching devices consisting of glass rods the stretching can be produced by pairs of rollers, the first roller of which has a smaller peripheral velocity then the second.

The draught roller, arranged behind the waterthe water, diminished by the contraction actually occurring. If the velocity with which the thread leaves the water be smaller than that with which it enters, less the amount of contraction, the threads will collect in the bath. The draught from the water-bath will preferably be a little higher than corresponds with the greatest contraction possible. Thereby the piece of thread immersed in the contraction bath will be somewhat lifted out of the bath, and the length of immersion will consequently be shortened, so that the contraction is correspondingly diminished and the speed of draught somewhat increased. The contraction and the two speeds of draught thus balance each other in such a way that under determined conditions of draught the thread passes through the water of the contraction bath with a determined length of immersion.

The water-bath may have room temperature or may be warmed. In the water of the contraction bath there can be dissolved substances which do not impede the contraction but even promote it.

In another mode of operation the thread contracted by passing through the water-bath is wound, in a completely unstretched state, on bobbins or reels and is stretched only in another step of the process so as to produce its final titre, while being simultaneously strengthened. Thereafter the thread can. be twisted, for instance in a spinning centrifuge. In this case it is most advantageous to stretch it in a wet state.

It is also possible to begin with washing and drying the thread wound in an unstretched state on bobbins or reels and then to stretch the dry thread so as to obtain its final titre while it is simultaneously strengthened, in which case twisting may follow immediately. Such contracted threads have in an unstretched state on elongation up to 30 to 50 per cent. or more when dry and an elongation up to 100 per cent. when wet.

The degree of the contraction and of the subsequent re-stretching depends upon the spinning bath used and upon the viscose. Therefore, it is not possible to obtain the same good results in all cases. At any rate higher elasticities are obtained with the same tenacities when using the same baths but with interposition of a contracting operation. It must be tested in each particular case, by what stretching before or behind the contraction bath the best results are obtained. Baths which are relatively poor in acid and rich in salts give, as a rule, better results if ripened viscose is spun, whereas other baths, for instance those prepared according to U. S. Patent No. 1,876,890 give good results under the most varied conditions. The viscose may be prepared from ripened as well as from unripened alkali cellulose. This improvement in the elasticity of the thread is associated with a considerably higher dyeing capacity of the fiber, so that, as compared with the ordinary viscose silks, no difference exists in the absorption of dycstuff. The process is suitable for the production of fiber bundles, which are made into staple fiber, as well as for the production of artificial silk.

It has already been proposed to draw freshly spun artificial threads from the bath at a determined speed and to wind them on a collecting device at a reduced speed. It has also been proposed to stretch the thread between two rollers running at different speeds, to wash it on the second roller with a liquid and to draw it off, if any contraction should thereby occur, by means of a third roller' having a smaller speed.

But the object of this invention is to allow the strongly stretched thread which hangs freely, to contract and to subject it again to be a stretching process. Small resistances suflice already to prevent the effect of the tendency to contract which is peculiar to the fiber.

The following examples illustrate the invention:

Example 1.--A viscose containing 5 per cent. of cellulose and 5.5 per cent of NaOH is spun at an ammonium chloride point of 9.5 cc. (determined with ammonium chloride of 15 per cent. strength) through a nozzle having 120 openings in a sulfuric acid bath of 76 per cent. strength heated to about 22 C. The quantity of the viscose delivered amounts to 7.9 cc. per minute and the last draught is adjusted so that the thread has a total titre of 120 deniers. After leaving the bath the thread passes over 3 glass rods of 1 mm. diameter and then over a roller whose peripheral velocity is 50 metres, round which it is wound once. From this roller its runs into a water-bath of an ordinary temperature in which it is immersed in a freely suspended state for a length of 20 cm. From this waterbath it is drawn off by a bobbin whose peripheral velocity is 33 metres. It is stretched between the waterbath and thebobbin by the interposition of 4 parallel glass rods of 5 mm. diameter, arranged in one plane. The spool runs in an upper bath containing water. When finished the threads have a tenacity of 3.54 grams per denier when dry, and 2.16 grams when wet, and an elongation of 9.2 per cent. when dry, and of 8.7 per cent. when wet.

Example 2.--The same viscose is spun at a rate of 8.15 cc. per minute into a bath of sulfuric acid of 65 per cent. strength heated to about 45 C., the first draught roller having a peripheral velocity of 54 metres, the spool having a peripheral velocity of 34 metres. The length of thread immersed in the contracting bath is 13 cm. Behind the contracting bath the thread is stretched by means of 3 glass rods of 5 mm. diameter. The temperature of the contracting bath is 30 C. The other conditions are the same as in Example 1. There are obtained threads whose tenacity in the dry state is 3.1 grams per denier and in the wet state 1.76 grams per denier and whose extensibility is 12.9 per cent in the dry state and 15.5 per cent. in the wet state.

Example 3.-The same viscose is spun at a rate of 7.65 cc. per minute into a bath kept at a temperature of 10-12 0., made by esterifying 20 parts of methanol with parts of concentrated sulfuric acid. The peripheral velocity of the first roller is 46 metres, that of the spool is 32 metres. The length of thread immersed in the contracting bath is 15 cm. the temperature of the latter is 18 C. Behind the contracting bath the thread is stretched over 2 rods only. The other conditions are as in Example 1. The threads obtained have a tenacity of 3.28 grams per denier in the dry state and of 2.26 grams per denier in the wet state and an elongation of 9.6 per cent. when dry and of 13.4 per cent. when wet.

Example 4.-The same viscose is spun at a rate of 7.2 cc. per minute into the same bath as in Example 3, with the difference that 10 per cent. of water is added to the spinning bath. The peripheral velocity of the draught roller is 49 metres, that of the spool is 30 metres. The temperature of the spinning bath is 23 C.; the

. by means of 4.rods. The other conditions are thread is stretched behind the contracting bath the same as those of Example 3. The threads obtained have a tenacity of 3.54 grams per denier when dry, and of 2.25 grams when wet, and an elongation of 11.2 per cent. when dry and of 12.6 per cent. when wet.

Example 5 .--There are used the same viscose and the same acid as in Example 3, except that there is added 20 per cent. of water. The peripheral velocity of the first draught roller is 50 metres, that of the spool is 30 metres. The other conditions are the same as in Example 4. The

threads obtained have a tenacity of 3.1 grams per denier when dry and of 1.73 grams when wet, and an elongation of 15 per cent. when dry and of 21.2 per cent. when wet. When winding up the threads after washing without tension and merely washing and drying the same they show an extensibility of about 50 per cent. in the dry state and about 100 per cent. in the wet state.

Example 6.-A ripened viscose containing 5 per cent. of cellulose and 5.5 per cent. of NaOH is spun with a salt point of 4.75 cc. and at a rate of 7.65 cc. per minute into a bath kept at 22 0., containing 44.35 per cent. of sulfuric acid, 26.8 per cent. of ammonium bisulfate and 3.4 per cent. of sodium bisulfate (per cent. by weight.) The temperature of the contracting bath is 35 C. Behind the contracting bath the thread is stretched by means of 3 glass rods. The peripheral velocity of the draught roller is 52 meters, that of the spool is 32 metres. The other conditions are the same as in the pr ceding examples. The threads have a tenacity of 3 grams per denier when dry and of 1.5 grams per denier when wet. The elongation is 13.7 per cent. when dry and 19.2 per cent. when wet.

The accompanying drawing illustrates a device adapted for executing our process.

The viscose is ejected through the spinning nozzlefl) into the precipitating bath (2). The precipitated thread is drawn off from the spinning bath by means of aroller (4) after having passed the glass rods (3) (Fig. 1) which serve as a stretching device. In Fig. 2 the glass rods 3 and I of Fig. 1 have been replaced by rollers Ii and 12 which rotate at a lower peripheral velocity than the rollers 4 and 9 thus forming a stretching device with the latter. The thread is wound one time around the roller (4) and guided by means of the thread guide (5). Coming from the roller (4), the threads drops into theshrinking bath (6), through which the threadpasses while sagging. whereupon itis guided over the glass rods (1) serving as a sec- 0nd stretching device. The thread is then wound on the bobbin (9) rotating in a washing bath (III), by means of the thread guide (8). Our invention is not limited to the foregoing examples nor to the specific details given therein. Numerous other embodiments are possible and we contemplate as included within our invention all such modifications and equivalents as fall within the scope of the appended claims.

What we claim is:

1. A process which comprises spinning viscose into a precipitating bath, adapted for spinning artificial silk of high tenacity, subjecting the freshly precipitated thread to a stretching operation, guiding the thread through a shrinking bath while sagging, and subjecting the thread to a second stretching operation while still moist.

2. A process which comprises spinning viscose into a precipitating bath adapted for spinning artificial silk of high tenacity, subjecting the freshly precipitated thread to a stretching p eration, guiding the thread through a bath while sagging and subjecting the thread to a second stretching operation immediately after having passed the shrinking bath and while employing a lower stretch than in the first stretching operation.

3. A process which comprises spinning viscose into a precipitating bath adapted for spinning artificial silk of high tenacity, subjecting the freshly precipitated thread to a stretching operation, guiding the thread through a shrinking bath while sagging, and subjecting the thread to a second stretching operation immediately after having passed the shrinking bath.

4. A process which comprises spinning viscose into a precipitating bath adapted for spinning artificial silk of high tenacity, subjecting the freely precipitated thread to a stretching operation, guiding the thread through a shrinking bath while sagging, and subjecting the thread to a second stretching operation after having been washed but in a still wet state.

5. A device for producing artificial threads of high tensile strength and high extensibility which comprises in operative combination a spirming bath, a first stretching device, a shrinking bath, and a second stretching device.

s. Artificial silk threads of cellulose hydratefio 

